// This file is derived from the NVIDIA CUDA SDK example 'MersenneTwister'.

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#ifndef BUDDHABROT_MERSENNETWISTER_CU_H
#define BUDDHABROT_MERSENNETWISTER_CU_H

#include "MersenneTwisterInternal.h"

#define MT_MM     9
#define MT_NN     19
#define MT_WMASK  0xFFFFFFFFU
#define MT_UMASK  0xFFFFFFFEU
#define MT_LMASK  0x1U
#define MT_SHIFT0 12
#define MT_SHIFTB 7
#define MT_SHIFTC 15
#define MT_SHIFT1 18

struct MersenneTwisterState {
	unsigned int mt[MT_NN];
	int iState;
	unsigned int mti1;
};

__device__ static mt_struct_stripped MT[MT_RNG_COUNT];

__device__ void MersenneTwisterInitialise(MersenneTwisterState &state, unsigned int threadID) {
	state.mt[0] = MT[threadID].seed;
	for(int i = 1; i < MT_NN; ++ i) {
		state.mt[i] = (1812433253U * (state.mt[i - 1] ^ (state.mt[i - 1] >> 30)) + i) & MT_WMASK;
	}

	state.iState = 0;
	state.mti1 = state.mt[0];
}

__device__ unsigned int MersenneTwisterGenerate(MersenneTwisterState &state, unsigned int threadID) {
	int iState1 = state.iState + 1;
	int iStateM = state.iState + MT_MM;

	if(iState1 >= MT_NN) iState1 -= MT_NN;
	if(iStateM >= MT_NN) iStateM -= MT_NN;

	unsigned int mti = state.mti1;
	state.mti1 = state.mt[iState1];
	unsigned int mtiM = state.mt[iStateM];

	unsigned int x = (mti & MT_UMASK) | (state.mti1 & MT_LMASK);
	x = mtiM ^ (x >> 1) ^ ((x & 1) ? MT[threadID].matrix_a : 0);
	state.mt[state.iState] = x;
	state.iState = iState1;

	// Tempering transformation.
	x ^= (x >> MT_SHIFT0);
	x ^= (x << MT_SHIFTB) & MT[threadID].mask_b;
	x ^= (x << MT_SHIFTC) & MT[threadID].mask_c;
	x ^= (x >> MT_SHIFT1);

	return x;
}

#endif
